Apache Tomcat: Security constraint bypass with HTTP/0.9
Improper Input Validation vulnerability in Apache Tomcat. Tomcat did not limit HTTP/0.9 requests to the GET method. If a security constraint was configured to allow HEAD requests to a URI but deny GET requests, the user could bypass that constraint on GET requests by sending a (specification invalid) HEAD request using HTTP/0.9. This issue affects Apache Tomcat: from 11.0.0 through 11.0.14, from 10.1.0 through 10.1.49, from 9.0.0 through 9.0.112. Older, EOL versions are also affected. Users are recommended to upgrade to version 11.0.15 or later, 10.1.50 or later or 9.0.113 or later, which fixes the issue.
02 / AFFECTED SOFTWARE
Affected packages
413 explicit affected versions
63 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
Improper Input Validation vulnerability in Apache Tomcat. Tomcat did not limit HTTP/0.9 requests to the GET method. If a security constraint was configured to allow HEAD requests to a URI but deny GET requests, the user could bypass that constraint on GET requests by sending a (specification invalid) HEAD request using HTTP/0.9. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.14, from 10.1.0-M1 through 10.1.49, from 9.0.0.M1 through 9.0.112. Older, EOL versions are also affected. Users are recommended to upgrade to version 11.0.15 or later, 10.1.50 or later or 9.0.113 or later, which fixes the issue.
Improper Input Validation vulnerability in Apache Tomcat. Tomcat did not limit HTTP/0.9 requests to the GET method. If a security constraint was configured to allow HEAD requests to a URI but deny GET requests, the user could bypass that constraint on GET requests by sending a (specification invalid) HEAD request using HTTP/0.9. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.14, from 10.1.0-M1 through 10.1.49, from 9.0.0.M1 through 9.0.112. Older, EOL versions are also affected. Users are recommended to upgrade to version 11.0.15 or later, 10.1.50 or later or 9.0.113 or later, which fixes the issue.
Improper Input Validation vulnerability in Apache Tomcat. Tomcat did not limit HTTP/0.9 requests to the GET method. If a security constraint was configured to allow HEAD requests to a URI but deny GET requests, the user could bypass that constraint on GET requests by sending a (specification invalid) HEAD request using HTTP/0.9. This issue affects Apache Tomcat: from 11.0.0 through 11.0.14, from 10.1.0 through 10.1.49, from 9.0.0 through 9.0.112. Older, EOL versions are also affected. Users are recommended to upgrade to version 11.0.15 or later, 10.1.50 or later or 9.0.113 or later, which fixes the issue.
05 / REFERENCES
Further evidence
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/24xxx/CVE-2026-24733.json
- https://lists.apache.org/thread/6xk3t65qpn1myp618krtfotbjn1qt90f
- https://nvd.nist.gov/vuln/detail/CVE-2026-24733
- https://github.com/apache/tomcat
- https://github.com/apache/tomcat/commit/2e2fa23f2635bbb819759576a2f2f5e64ecf7c5f
- https://github.com/apache/tomcat/commit/6c73d74ff281260d74c836370ff6b82f1da8048b
- https://github.com/apache/tomcat/commit/711b465cf22684a1acf0cb43501cdbbce9b6c5f4
- https://tomcat.apache.org/security-10.html
- https://tomcat.apache.org/security-11.html
- https://tomcat.apache.org/security-9.html